Subject Re: Firebird 2.5.2.26540 superclassic on Ubuntu 14.04 LTS Server
Author
How this command does it look 

sudo netstat -tap -n  | grep firebird 
   
it should look something like 
tcp        0      0 0.0.0.0:3050            0.0.0.0:*               LISTEN      1566/firebird


also you should check iptables rules
sudo iptables -L